1. Field of the Invention
The present invention relates to the field of drilling devices, and more specifically, to drilling devices with turbine propulsion.
2. Prior Art
As the world's supply of natural resources diminishes, greater efforts are being required to recover such resources. For example, with the diminishing supply of crude oil and natural gas, greater efforts have been required to recover these minerals. Thus, well drilling to greater depths to recover minerals has been necessitated. However, the increased formation of pore fluid pressures existing at great depths in the earth's crust, adversely affects current drilling methods. Also, with the increased distances involved in drilling at great depths, it has been difficult to effeciently supply adequate energy to the drilling site.
One prior art attempt to generate energy close to the drilling site is a turbine drill wherein hydraulic turbines are utilized. In these devices, the rotor of the turbine is directly coupled with the roller bit, and the fluid used to activate the turbine, the working fluid, is expelled so that it can be used to flush drilling debris up and away from the drilling device. One problem with such turbine drills is that their efficiency of operation is not independent of the depth at which the drilling device is being used. That is, as the drilling device is being lowered to greater depths, it takes a greater amount of energy to generate and expel the working fluid. Another problem with such turbine drills is their vulnerability to damage caused by rocks and other debris which is suspended in the working fluid. Since the working fluid is used to activate the turbine, the turbine and its associated feed mechanisms are subject to severe damage. A further problem both with the prior art hydraulic turbine drills and with earth drilling devices in general is the vulnerability of the drill bits they utilize. That is, the prior art devices only provide a constant force and drill bit rotation rate. As these drill bits bore through material which varies in both density and hardness, the unregulated force and rotation rate frequently results in broken bits. What is needed is a turbine drilling device which can be operated at great depth with a high energy output but without a loss of efficiency or susceptibility to damage.
In the present invention, the problems of efficiency loss at great depths have been eliminated by the utilization of an energy generating system which requires little energy for the expulsion of exhaust gasses, and a closed fluid circuit in conjunction with a turbine drilling device. More specifically, the energy generating system, which is disposed in a drilling lance, utilizes combustion techniques which produce little waste gasses. Thus, only a minimum amount of energy is required to expel such gasses, even at great working depths where the external pressures are high. The generating system comprises a fluid vaporizing system and a turbine coupled to the vaporizing system by a closed fluid circuit. That is, the fluid utilized in activating the turbine is not expelled from the device but is recirculated in a closed circuit. In the configuration of the present invention, the combustion process, the fluid vaporizing system, and the turbine coupled to the vaporizing system, operate virtually independently of external pressures.
The present invention allows a self-contained energy generating system to be lowered directly to the drilling site. By this approach, no energy is required to force fuels to great depths where these devices are being utilized, while a high power density can be generated directly at the drilling site. Furthermore, since the fluid utilized to activate the turbine is not drawn from the working fluid surrounding the drilling device, damage to the turbine from debris is virtually eliminated. This allows the present invention to have a longer time between failures and a greater life span. In addition, the energy generating system, the drilling means, and the force applied to the drilling means are controlled by a control means. This control means senses various parameters and regulates the drilling rate and energy expended so that maximum drilling efficiency is maintained. Through this control means, variations in drilling material density and hardness may be sensed and compensated for so that the life of the drilling means is greatly increased.